Dichloromethylation of xylenes



United States tt DICHLOROMETHYLATION F XYLENES William G. De Pierri, Jr., and Harold W. Earhart, Baytown, Tex., assignors, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, N.J., a corporation of Delaware No Drawing. Filed Oct. 9, 1958, Ser. No. 766,178

4 Claims. (Cl. 260-651) This invention relates to a process for the dichloromethylation of xylenes. More particularly, this inven- 2,964,573 Patented Dec. 13, 1960 EXAMPLE I A plurality of samples of orthoxylenes were chloromethylated under a variety of chloromethylation conditions. The chloromethylation conditions employed and the results obtained are set forth in the following table.

Table I DICHLOROMETHYLATION OF o-XYLENE Experiment No 1 2 3 4 5 6 7 8 9 Mols HCl/Mol o-Xylene 2 10 4% 7 3 14 5 3% 6 Mols ZnClz/Mol o-Xylene 3 1 $4 1% 2 1 $4; 1 Mols OHzO/MO]. o-Xylen 2 6 1% 3 2%; 5 2 1% 4 Mols H2O/M0l o-Xylene. 11 70 25 60 23 50 Time, Hr 1 1 4 1 1% 1% A 1% 14 Temperature, C 95 85 85 75 85 95 95 75 75 Product, Percent:

o-Xylene 69. 7 31. 8 34. 7 28. 0 56. 2 0. 4 69. 1 64. 7 87. 9

Ohloromethyl-o-xylene 22. 1 42. 7 38. 8 59. 9 25. 1 48. 7 27. 1 5. 9 5. 6

Dlehloromethyl-o-xylene 2. 1 10. 6 4. 5 2. 5 38. 3 1. 1 1. 9

Trichloromethyl-o-xylene 0. 1 0. 4 1. 8

Tetrachloromethyl-o-xylone 3. 1'

tion relates to a process for the conversion of xylenes to dichloromethyl xylenes with high yield and high selectivity.

In copending application Ser. No. 717,225 for H. W. Earhart et al., filed February 24, 1958, and entitled Chloromethylation Process, noW abandoned, there is disclosed a process for chloromethylating aromatic hydrocarbons in a manner to minimize the formation of unwanted alkyl diphenyl methane by-products. While highly beneficial results are obtainable With the process disclosed in the said copending application, problems are encountered in dichloromethylating xylenes when the desired product is to be composed primarily of the dichloromethylated product.

It has now been surprisingly discovered that maxi- EXAMPLE II A plurality of samples of paraxylene were subjected to chloromethylation under a Wide variety of reactions. The conditions employed and the results obtained are mized yields and selectivities of dichloromethyl xylenes set forth in Table H.

Table II DICHLOROMETHYLATION OF p-XYLENE Experiment N0 1 2 3 4 5 6 7 8 9 Mols HOl/Mol p-Xylene... 2 10 4% 7 3 14 5 3% 6 Mols ZllOlz/MOI p-Xylene. 3 1 M; 135 2 1 14 1 Mols CHzO/Mol p-Xylene. 2 6 1% 3 2% 5 2 1% 4 Mols HgO/Mol p-Xylene 11 20 30 25 60 35 23 50 Time, Hr 1 1 $4 1 1% 1% $2 1% l Temperature, C 95 85 85 95 75 75 Product, Percent.

p-Xylene 83. 2 47. 4 42. 9 36. 2 70. 4 1. 2 79. 3 88.0 93. 9

Chloromethyl-pxylene 14. 6 43. 6 31. 9 56. 2 21. 0 66. 0 19. 2 6. 0 2. 8

Dichloromethyl-p-xylene 2. 2 9. 0 5. 2 5. 7 4. 8 28. 2 1. 5 1. 1 0; 7

Triohloromethyl-p-xylene 0. 5 0. 4

Tetrachloromethyl-p-xylene 0. 5

A plurality of samples of metaxylene were subjected to a variety of chloromethylation conditions. The experimental conditions employed and the results obtained are set forth in Table III.

which comprises contacting said xylene with about 12 to mols of hydrochloric acid, about 1.5 to 2.5 mols of zinc chloride, about 4.5 to 5.5 mols of formaldehyde, and about 55 to 65 mols of water per mol of xylene at a temperature of about 90 to 100 C. for a reaction time Within the range of about 1 to 3 hours and thereafter recovering a dichloromethyl xylene from said product.

2. A method as in claim 1 wherein the xylene is orthoxylene.

3. A method as in claim 1 wherein the xylene is metaxylene.

4. A method as in claim 1 wherein the xylene is paraxylene.

Table 111 DICHLOROMETHYLATION OF m-XYLENE Experiment N0 1 2 3 4 5 6 7 8 9 Mols HCl/Mol m-xylcne 7 6 14 4. 7 10 3. 3 5 2 3 Mols ZIlClg/MOI m-xylene 0.5 1 2 1 3 0.3 1 0.7 1.5 Mols CHzO/MOI rn-xylene 3 4 5 1. 8 6 1. 7 2 2 2.5 Mols H2O/M01 m-xy1ene- 20 23 35 11 25 Time,Hr 1 0.5 1.5 0.5 1 1.5 0.5 1 1.5 Temperature, C 75 95 85 75 95 85 Product, Percent:

Monochloromethyl 79.0 45.4 2.0 64.5 43.5 44.2 58.9 36.0 25.0

Dichloromethyl 15.7 41.9 84.9 21.1 33.4 1.8 8.8 7.9 13.6

Dlphenylmethanes and Trlcbloromethyl 0.5 3.1 8.5 7.2 19.4 1.4 6.6 29.2 51.7

From Table III it will again be observed that a maxi- 30 References Cited in the file of this patent mized yield of the dichloromethyl product was obtained UNITED STATES PATENTS only in the case of Run No. 3 conducted in accordance 2 469 334 Hanough t al Ma 3 1949 with the resent invention. The results obtained with e y p 2,862,980 Muench et a1. Dec. 2, 1958 metaxylene are particularly surprising. Note that with metaxylene the chloromethylation product that is obtained consists essentially of dichloromethyl-meta-xylene and that only minor amounts of monochloromethyl-metaxylene are formed.

Having described our invention, what is claimed is:

OTHER REFERENCES Ginsburg et al.: Ind. and Eng. Chem., vol. 38, pages 478-485 (1946).

Adams et al.: Organic Reactions, vol. I, pages 64-70 1. A method for the dichloromethylation of a xylene 40 (1942). 

1. A METHOD FOR THE DICHLOROMETHYLATION OF A XYLENE WHICH COMPRISES CONTACTING SAID XYLENE WITH ABOUT 12 TO 15 MOLS OF HYDROCHLORIC ACID, ABOUT 1.5 TO 2.5 MOLS OF ZINC CHLORIDE, ABOUT 4.5 TO 5.5 MOLS OF FORMALDEHYDE, AND ABOUT 55 TO 65 MOLS OF WATER PER MOL OF XYLENE AT A TEMPERATURE OF ABOUT 90* OF 100*C. FOR A REACTION TIME WITHIN THE RANGE OF ABOUT 1 TO 3 HOURS AND THEREAFTER RECOVERING A DICHLOROMETHYL XYLENE FROM SAID PRODUCT. 